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CHAPTEE IX
UNGULATA----CONDYLARTHRA----AMBLYPODA—ANCYLOPODA—
TYPOTHEEIA—TOXODONTIA—PliOBGSCIDEA----HYEACOIDEA
I¥.
THE existing members of this order can be readily grouped
into the Hyracoidea, Proboscidea, Perissodactyla, and Artiodactyla,
each of which divisions has quite the value of an order, and all of
which are sharply marked off from each other. But as the dis-
covery of so many fossil forms has to a great extent rendered
these demarcations less sharp, it is better to regard all these
groups as not more than sub-orders of a larger " Order " Ungulata.
Even when this conclusion has been necessarily arrived at from
a consideration of the more ancient groups of Ungulate animals,
the definition of such an order remains a difficult matter for
the systematise For the earliest of these forms, more particu-
larly the Ancylopoda, the Amblypoda, and the Condylarthra,
whose peculiarities will be dealt with at length subsequently,
are not by any means easily differentiated from the primi-
tive Carnivorous mammals of that date, the Creodonta; these
latter, moreover, fade into the Marsupials through the so-
called Sparassodonta of Professor Ameghino. To confine our-
selves to the Ungulates, we may perhaps define them as terres-
trial animals with hoofs rather than claws or nails, and chiefly,
if not entirely, vegetarian in habit. The teeth are bunodont or
lophodont, the tendency to the production of the latter type being
always marked. The walk, although plantigrade in the older types,
becomes more and more digitigrade, except in such survivals from
antiquity as Hyratt. There isj too, as we pass from the ancient
types to the modern, a gradual perfection of the limbs as running